In a new study, 27 percent of children and teens underestimated their weight. Fewer than 3 percent overestimated it. About 25 percent of parents underestimated their child’s weight and just 1 percent overestimated it, according to the study.

“Efforts to prevent childhood obesity should incorporate education for both children and parents regarding the proper identification and interpretation of actual body weight,” said lead researcher Han-Yang Chen, from the department of quantitative health sciences at the University of Massachusetts Medical School in Worcester, Mass.

“Interventions for appropriate weight loss should target children directly because one of the major driving forces to lose weight comes from the child’s perception of their weight,” he said.

The report was published July 31 in the journal Preventing Chronic Disease.

Dr. William Muinos, director of the weight management program at Miami Children’s Hospital, said, “I see weight misperception all the time.”

Parents don’t understand why their child is overweight or obese, he said. Parents think their child has a glandular problem or they will outgrow obesity. “That’s nonsense, because obese kids are likely to stay obese,” Muinos said.

Children can misperceive their weight if all the people they see are obese or overweight, he said. “If everyone you’re around in your family and your social world is obese or overweight, then you are one big happy family. And you see that in our country,” Muinos explained.

For the study, Chen’s team used data from the 2007 to 2008 and 2009 to 2010 National Health and Nutrition Examination Survey to assess weight perceptions. The surveys included more than 2,500 kids aged 8 to 15 years.

The researchers found that the odds of trying to lose weight was nearly 10 times higher among participants who overestimated their weight than among those who perceived their weight accurately. Those who underestimated their weight were the least likely to attempt to lose weight, according to the study.

Parental misperception of weight was not associated with attempts to lose weight among children and teens who were overweight or obese, the investigators found.

Dr. David Katz, director of the Yale University Prevention Research Center, takes a broader view of the problems of weight perception.

“Above all, this study highlights the perils of a societal preoccupation with weight, rather than a focus on health and the lifestyle factors that support it,” he said.

Eating well and being active are important regardless of weight because they promote health, he said. “Weight is merely one among many measures that suggest something about overall health, albeit an important one,” Katz said.

The high rate of dieting among children who overestimated their weight is of real concern, he noted. “This behavioral pattern suggests impaired body image perception and vulnerability to eating disorders,” Katz said.

The more common problem of underestimating weight and its effect on lowering the likelihood of weight control efforts is also concerning, he added.

“These opposing problems are really two sides of the same coin — the fixation on weight rather than health. In general, dieting is ill advised, both for overweight children and those misperceiving their weight as high when it isn’t,” Katz said.

Eating well and being active are recommended for both groups and all other children, he said. “We do need to raise awareness about the importance of childhood obesity, but we need to emphasize that what really matters is health,” Katz explained.

“If a devotion to healthful behaviors was the norm in our culture, and not the perception of weight, we would not talk our children into dieting they do not need, or out of weight control efforts they do need,” he said.

Muinos added that parents need to be educated about the importance of healthy eating and exercise as well as the dangers of obesity.

Getting children to eat well and exercise needs to be a family effort, Muinos said. “You cannot isolate the child who is obese. The whole family has to be involved both in exercise and diet,” he said.